Audi A4 Avant 95-01 Service & Repair Manual

01-1

A/C system, On Board

Diagnostic (OBD)

Function

The A/C control head -E87- receives input

information from various electrical and electronic

components (sensors).

This information is processed by the control head

in accordance with specified values and then

provides corresponding output signals that

control electrical components (actuators).

The control head is controlled by an internal

microprocessor with On Board Diagnostic (OBD)

capability. If faults or open circuits occur on

applicable components, Diagnostic Trouble

Codes (DTC) are stored in DTC memory. Stored

faults are identified using either VAG1551 Scan

Tool (ST) or VAG1552 Scan Tool (ST). Tables

containing all DTCs and corresponding repair

information guide technicians through the OBD

process.

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01-2

Notes:

This Repair Manual describes On Board

Diagnostic (OBD) with VAG1551 Scan Tool

(ST). OBD procedures can also be performed

with VAG1552 Scan Tool (ST) (VAG1552 Scan

Tool is not equipped with a printer).

Scan Tool VAG1551 or 1552 must be used in in

operating mode -1- (Rapid data transfer).

Operating mode -2- (Flash code output) is not

provided for A/C and Heating OBD.

Always check DTC memory and perform

necessary repairs before erasing DTC memory.

DTC output is possible only if ignition is on or

engine is running and engine speed is less than

3000 rpm (if engine speed is higher, output is

possible only for a limited time or is terminated).

If a fault exists for a certain time it is stored as a

static fault.

If a static fault is no longer present after a

certain time, it is stored as a sporadic fault and

the reference "SP" appears on the upper right

of the VAG1551 display/print-out.

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Before replacing a suspected malfunctioning

component, check all related wiring,

connections, harness connectors and Ground

(GND) connections according to the appropriate

wiring diagram.

Output Diagnostic Test Mode (DTM), Basic

Setting, A/C control head identification and

coding functions are also possible.

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01-3

Notes:

A/C system component locations: engine

compartment page 87-96 .

A/C system component locations: passenger

compartment page 87-106 .

If a the display of a newly installed A/C control

head -E87- flashes after switching the ignition

on (for approximately 2 minutes), code the

control head page 01-57 and execute basic

setting page 01-52 .

If a replacement control head is not coded after

installation or if an unrecognized code was

entered, code "00042" (4-cyl. gasoline engine

USA) is stored.

Control of A/C compressor, flap motors and fan

motors etc. is not possible when executing

Output Diagnostic Test Mode (DTM), function

03 and basic setting, function 04. A/C control is

possible in all other functions.

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01-4

Heating and A/C system changes, 1997

On Board Diagnostic changes

New A/C control head -E87- with specific

coding for m.y. 1997, 4-cyl. and 6-cyl. engines.

Notes:

Before performing On Board Diagnostic of A/C

system, ensure A/C control head -E87- is coded

correctly (according to engine application).

A/C control heads beginning with Part No. 8L0

820 043 should only be installed in m.y. 1997

vehicles.

A/C control heads beginning with Part No. 8D0

820 043 must only be installed in vehicles

through m.y. 1996.

CAUTION!

Part numbers are for reference only.

Always check with your Parts Dept. for the

latest information.

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01-5

Notes:

For m.y. 1997, changes that affect monitoring of

the A/C system by A/C control head -E87- were

made.

Monitored components, locations pages 87-

101 and Page 87-113 .

Additional technical data and notes page 01-

1 .

If a replacement A/C control head is not coded

after installation or if an unrecognized code was

entered, code "04142" (Audi A4 -4cyl. -USA) is

stored.

The A/C control head is no longer connected to

terminal 30 (vehicle electronics). The last input

setting (into the A/C control head) is stored

when the ignition is switched off and retained

when the ignition is switched on.

The duration of time when ignition is off is

calculated by the A/C control head. When

ignition is switched on, the previous "standing

time" is calculated by monitoring a time signal

from the instrument cluster. If more than 4

hours pass since ignition was switched off, the

actual measured values of the outside

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temperature sensor are used as instantaneous

outside and engine temperature inputs for A/C

system control. If "standing time" is shorter than

4 hours, the actual measured values of the

outside temperature sensor are suppressed

and system output temperature control is

calculated by the A/C control head. The

"standing time" period is monitored and used

for this calculation. (Heat radiating from the

engine and radiator leads affects the measured

value of the temperature sensor).

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01-6

The following components previously monitored

by OBD and triggered by A/C control head -E87-

are deleted:

Refrigerant low pressure switch -F73-.

Refrigerant high pressure switch -F118- (low

and high pressure switch functions integrated

into A/C pressure switch, -F29-).

Fresh air/recirculating flap two-way valve -

N63-.

The following new components are monitored by

OBD and provide input signals to -E87-:

A/C pressure switch -F129-.

Sender for outlet temperature, center -G191-.

Sender for outlet temperature, floor outlet -

G192-.

The following components monitored by OBD or

triggered by -E87- are revised:

The heater/air conditioner assembly with all

servo motors.

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The fresh air blower and control module.

Following components that provide input signals

to the A/C control head -E87- are revised:

Instrument cluster

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01-7

A/C system changes

Revised heating/air conditioner assembly with

flap motors page 87-174 .

The air flow flap motor now activates the fresh

air/recirculating air flap as well.

The two way valve for the circulating/fresh air

door, the vacuum unit and the vacuum reservoir

are deleted.

A/C refrigerant circuit changes

New service valve connection on low pressure

side.

Service valve connection for high pressure side

installed in high pressure line in plenum panel

(deleted at condenser).

A/C pressure switch -F129- replaces pressure

switches -F73- and -F118-.

New version "Zexel" compressor and high

pressure line (4-cyl. engines only).

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01-8

VAG1551 Scan Tool (ST), connecting;

A/C control head -E87-, checking

version

Battery Voltage OK

Fuse 22 (S22) OK

Ground (GND) connection on engine and

transmission OK

1996 vehicles

- Open rear passenger ashtray in center console and remove cover for

Data Link Connector (DLC).

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01-9

- With ignition switched off, connect VAG1551 Scan Tool (ST) to Data

Link Connector (DLC) with cable VAG1551/3.

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01-10

1997 vehicles

All vehicles

- With ignition switched off, connect VAG1551 (VAG1552) scan tool to

16-pin Data Link Connector (DLC) under dash to left of steering

column, using adapter cable VAG1551/3.

V

.A.G - ON BOARD DIAGNOSTIC HELP

1 - Rapid data transfer

2 - Blink code output

Indicated on display 1)

1)

Operating modes 1 and 2 are displayed alternately

- Switch on printer with -PRINT- button (indicator lamp in switch will light

up).

- Switch on ignition or start engine.

- Switch A/C compressor on (press "AUTO" button).

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01-11

- Press button -1- for operating mode "Rapid data

transfer."

Rapid data transfer HELP

Enter address word XX

Indicated on display

Notes:

If display is blank, check wiring to VAG1551/power supply using

Troubleshooting Procedure No. 1 in "Electrical Wiring Diagrams,

Troubleshooting and Component Locations" Manual.

Address word for A/C Heating Electronics: 08

Additional operating instructions can be obtained by pressing the

HELP button on VAG1551 Scan Tool (ST)

During testing procedures, the button advances the program to the

next step

An incorrect entry can be cancelled with the -C- button

- Press buttons -0- and -8-.

Rapid data transfer Q

08 - A/C Heating Electronics

Indicated on display

- Press -Q- button to confirm input.

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01-12

If one of the following messages is displayed:

Rapid data transfer HELP

Control module does not answer

Indicated on display

or

Rapid data transfer HELP

K wire not switchin

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to B+

Indicated on display

- Press HELP button to print out list of possible causes.

Rapid data transfer

No si

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nal from control module

- Check wiring to Data Link Connector (DLC) according to wiring

diagram Electrical Wiring Diagrams, Troubleshooting & Component

Locations binder.

Rapid data transfer

Error in communication link

If this display appears at the beginning of or during the OBD program,

malfunctions have occurred and data transfer is no longer possible

between the VAG1551 Scan Tool (ST) and the A/C control head -E87-.

Electrical Wiring Diagrams, Troubleshooting & Component Locations

binder

- Check wiring to DLC.

Rapid data transfer Q

08 - A/C Heatin

g

Electronics

- After repairing possible causes of the malfunction, press buttons -0-

and -8- to insert "AC/Heating Electronics" address word 08.

- Press -Q- button to confirm input.

Rapid data transfer

Scan Tool sends address word 08

Indicated on display

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01-13

8D0820043D A4-Klimavollautomat DXX

Coding 00062 WSC ZZZZZ

Indicated on display after approx. 5 seconds

Readout example shows US/CDN version, Zexel A/C compressor, 6

cylinder gasoline engine

Coding -E87- and code tables page 01-57 .

8D0 820 043 D: Part Number of A/C control head -E87-

A4: A/C Heating Electronics component designation

DXX: Software version of A/C control head -E87-

Coding: 00062

WSC 06812: Dealership code

8L0 820 043B A4-

A

/C full

y

automatic DXX

Codin

g

XXXXX WSC ZZZZZ

For m.y. 1997 vehicles install only A/C control head -E87- with Part No.

8L0 820 043 up to and including Part No. index letter "C."

8L0 820 043D A4-

A

/C full

y

automatic DXX

Coding XXXXX WSC ZZZZZ

For vehicles beginning m.y. 1998 install only A/C control head -E87- with

Part No. 8L0 820 043 from Part No. index letter "D."

CAUTION!

Part numbers are listed here for reference only. Always check with

your Parts department for the latest information.

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01-14

Part

number

Comments

8D0 820

043 D - G

Regulation is only switched off in

On Board Diagnostic (OBD)

during output diagnostic test

mode and basic setting.

For vehicles with 6 cylinder

engines, must only be combined

with Zexel compressor.

8D0 820

043 after

H

For all vehicles up to m.y. 96.

8L0 820

043 A - C

For all vehicles up to m.y. 97 (lighting

via terminal 58 and 58d)

8L0 820

043 after

D

For all vehicles up to m.y. 98 without

radio navigation system up to VIN

199999 of m.y. 1999 (lighting

indirectly activated via terminal 58s).

8D0 820

043 K or L

Version with only one display (for

vehicles with radio navigation system

up to VIN 199999 of m.y. 1999)

8D0 820

043 after

M

Version with only one display (for

vehicles as of VIN 200000 of m.y.

1999)

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01-15

Notes:

Zexel A/C compressors were installed from

start of production. During m.y. 1996,

Nippondenso type compressors are installed as

a running change. These compressors are not

equipped with A/C speed sensor G111.

The A/C control head is coded to reflect the

compressor type installed (Zexel or

Nippondenso).

Vehicles equipped with Nippondenso (Denso)

compressors must have A/C control head with

Part No. index "H" or higher installed to allow

for correct coding.

Follow coding exactly when replacing an A/C

control head -E87-.

Parts catalog microfiche

A/C control head varies after VIN 200000 of

m.y. 1999 for vehicles with and without radio

navigation system (or a radio with a large

control panel), with and without switch for

heated seats (e.g. index "M", "N", "P" or "Q").

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Parts catalog microfiche

Depending on VAG1551 Scan Tool (ST)

p

rogram card version, 1st and 2nd digit may not

be displayed (readout: e.g. 040 instead of

00040).

Software version of control head is of no

significance for service department.

If a replacement control head is not coded after

installation or if an unrecognized code was

entered, code "00042" (4-cyl. gasoline engine

USA) is stored.

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01-16

Safety precautions

If special testing equipment is required during

road test, note the following:

WARNING!

Special testing equipment must always be

secured on the back seat and must be

operated from there by a 2nd person.

If special testing equipment were to be

operated from the passenger seat, there

could be injuries to the person seated there

in the event of an accident and air bag

deployment.

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Audi A4 Avant 95-01 Service & Repair Manual

Audi A4 Avant 95-01 Service & Repair Manual

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